The present invention pertains to impact borers for earth boring, to connectors, and to boring and drilling methods, and more particularly pertains to an impact borer, a connector, a method for embedding lines, anchoring cables, and sinking geothermal wells.
Impact borers push through soil by means of an internal air-operated hammer, which impacts against the body of the tool. The impacts move the tool forward incrementally, compacting and displacing soil and creating a tunnel. After tunneling, an impact borer may be recovered from the exit end of the tunnel. Recovery at the entry end is difficult or impossible in many instances, since an impact borer usually cannot be reversed and cannot be pulled backward out of a tunnel more than a few feet long.
Impact borers have commonly been used to tunnel horizontally under roads or other obstructions. After an impact borer has tunneled through to an exit pit or the surface, the borer is removed and detached from its supply hoses. Access is then available to the tunnel at either end, and pipe or conduit may be drawn through the tunnel.
Impact borers have had the shortcomings of being complex and expensive. This limits use to situations in which recovery is likely. This presents a barrier to use of impact borers for embedding lines such as guy wires and anchoring cables, sinking wells, and the like.
Use of an impact borer in any but a horizontal direction has been extremely inadvisable, since even when used horizontally, the direction of travel of an impact borer has not been entirely predictable. Encountered rocks can redirect or stop an impact borer, which must then be located and dug up for another try. Boundaries between soil layers, for example, between a layer of clay and a layer of sand, can have the same effect. Directing an impact borer downwardly rather than horizontally has presented a considerable risk of the borer stopping at an insufficient depth or turning and traveling horizontally in an unknown direction at an unknown depth.
It also has not been feasible to make impact borers or other implements subject to repeated impacts or very rough usage, or to join very high molecular weight polyethylene pipe to ultra high molecular weight polyethylene. Very high molecular weight (VHMW) polyethylene is strong and resistant to abrasion and degradation and is a material commonly used for pipe used in geothermal wells. Ultra high molecular weight (UHMW) polyethylene is an even tougher material used for some mechanical components. VHMW and UHMW polyethylene components may be weakly fused together by heating and then pressing the components together. However, it has not been feasible to join VHMW and UHMW polyethylenes in highly stressed or pressurized pipe joints, such as the joint between a VHMW pipe and a UHMW impact borer component which must withstand pulls exceeding the tensile strength of VHMW polyethylene. Another problem of such joints is that heated VHMW polyethylene pipe, upon insertion into a UHMW component tends to flow excessively and cause a partial blockage.
Commonly used well sinking methods such as forcing a bit forward with a jack or the weight of a pipe string or pulling pipe with a screw or a rearwardly directed jet have a variety of shortcomings. Many methods require heavy, rigid pipe strings. Some methods are limited to vertical use. Other methods are limited to particular soil types or depths. Impact driver methods, as noted above, are generally impractical for non-horizontal use. The greatest majority of methods require large, heavy machinery at the bore site.
These various shortcomings present a major problem in embedding lines, anchoring cables, and sinking wells including geothermal wells, i.e., wells used as heat sinks for heat pumps used for space heating and cooling and the like. In order to prevent ground water contamination, geothermal wells are generally required to limit circulation of water or other fluid to a closed loop of pipe. Plastic (VHMW polyethylene) pipe for that purpose is commonly dropped down vertical wells after drilling is completed. For practical reasons, a series of relatively shallow wells are generally dug rather than a single deep well. Generally, 150 feet of well is required for each ton of air conditioning. The individual wells are separated by a few feet to ensure that the "heat sinks" of soil surrounding each well do not significantly overlap. Pipe must be laid between each of the wells and a junction, which communicates with the heat pump. These connecting pipes must be buried or must be insulated to maintain system efficiency. Horizontal space taken up by the system is not small. This may not be critical in new construction, but along with space requirements of drilling equipment may preclude use in retrofitting existing buildings.
It is therefore highly desirable to provide an improved impact borer, an improved connector, an improved method for embedding lines, anchoring cables, and sinking wells.
It is also highly desirable to provide an improved impact borer, an improved connector, an improved method for embedding lines, anchoring cables, and sinking wells in which an impact borer is so inexpensive as to permit nonrecovery after use.
It is also highly desirable to provide an improved impact borer, an improved connector, an improved method for embedding lines, anchoring cables, and sinking wells effective in nonhorizontal use.
It is also highly desirable to provide an improved impact borer, an improved connector, an improved method for embedding lines, anchoring cables, and sinking wells in which pipes connected to the impact borer may be converted into a closed loop within a bore-hole.
It is also highly desirable to provide an improved impact borer, an improved connector, an improved method for sinking wells which provide an effective connector between VHMW and UHMW polyethylenes, such that VHMW polyethylene well pipe may be sunk by use of an impact borer.
It is also highly desirable to provide a improved impact borer, an improved connector, an improved method for embedding lines, anchoring cables and sinking wells which eliminates need for drilling rigs, tolerates space requirements and existing landscaping and buildings, reduces installation time and is ecologically preferable when compared to prior art apparatus and methods.
It is finally highly desirable to provide an improved impact borer, an improved connector, an improved method for embedding lines, anchoring cables, and sinking wells which meet all of the above desired features.